Isabelle
of France never met William Wallace
Isabelle of France was Prince Edward’s fiance, but at the time of
William Wallace’s military escapades, she was a mere four years old and
therefore couldn’t have physically met or been in contact with Wallace (even
though Wallace had travelled to France during the war to ask for assistance
against the English).
This obviously means that everything
she does in the film, help Wallace by informing him of the English Army’s
movements, the affair and giving him pain-numbing medicine before his execution
did not happen.
A more glaring incongruity might be that French was widely
spoken in the English court even around the time of Wallace, which means that
Isabelle and her handmaiden’s secret conversations in French, wouldn’t really
have been very secret at all.